Abstract:

In an intervertebral implant having an abutment element for abutment on at
least one vertebral body, in order to be able to apply pulling forces to
the abutment element without the risk of damage to the abutment element,
it is proposed that the abutment element carry at a side edge a pull
element which extends along the side wall of the abutment element and is
held on the abutment element by pull members extending at the sides of
the abutment element in the direction towards the opposite side edge, the
pull element being made of a material whose tensile strength is greater
than the tensile strength of the material of the abutment element, and
that an interspace for receiving a handling instrument engaging the pull
element from behind be arranged at least in a section along the pull
element between the pull element and the abutment element. A handling
instrument for handling such an intervertebral implant is also described.

Claims:

1. Intervertebral implant having an abutment element for abutment on at
least one vertebral body, said abutment element carrying at a side edge a
pull element which extends along the side wall of the abutment element
and is held on the abutment element by pull members extending at the
sides of the abutment element in the direction towards the opposite side
edge, said pull element being made of a material whose tensile strength
is greater than the tensile strength of the material of the abutment
element, and an interspace for receiving a handling instrument engaging
the pull element from behind being arranged at least in a section along
the pull element between said pull element and said abutment element.

2. Intervertebral implant in accordance with claim 1, wherein the
interspace is arranged in the central area of the side edge.

3. Intervertebral implant in accordance with claim 1, wherein the
interspace is formed by a recess in the abutment element, which is
bridged by the pull element.

4. Intervertebral implant in accordance with claim 2, wherein the
interspace is formed by a recess in the abutment element, which is
bridged by the pull element.

5. Intervertebral implant in accordance with claim 1, wherein the abutment
element has a depression above and/or below the pull element for
receiving in a guided manner a positioning projection on the handling
instrument.

6. Intervertebral implant in accordance with claim 1, wherein the pull
members are joined to one another at their ends facing away from the pull
element.

7. Intervertebral implant in accordance with claim 5, wherein the pull
members extend around the outer side of the abutment element and thereby
lie against its side walls.

8. Intervertebral implant in accordance with claim 1, wherein the pull
members extend inside the abutment element at their ends facing away from
the pull element.

9. Intervertebral implant in accordance with claim 6, wherein the pull
element and the pull members are formed by an annular bandage.

10. Intervertebral implant in accordance with claim 9, wherein the bandage
is in the form of a flat band.

11. Intervertebral implant in accordance with claim 1, wherein a
longitudinal groove for receiving the pull element and the pull members
is provided at the side walls of the abutment element.

13. Intervertebral implant in accordance with claim 1, wherein an abutment
element provided with a pull element consists of a plastic material.

14. Intervertebral implant in accordance with claim 1, wherein the
abutment element has an upper outer side and a lower outer side, which
are both constructed as surfaces for abutment on adjacent vertebral
bodies.

15. Intervertebral implant in accordance with claim 1, comprising an upper
abutment element and a lower abutment element, which are pivotable
relative to each other, said upper abutment element having an upper outer
side, and said lower abutment element having a lower outer side, which
are both constructed as surfaces for abutment on adjacent vertebral
bodies.

16. Handling instrument for an intervertebral implant in accordance with
claim 1, having two holding arms arranged in spaced relation to each
other, between which the intervertebral implant is arranged in such a way
that the holding arms lie against the upper side and the lower side of
the abutment element, and having mounted between the holding arms a slide
which is retractable relative to the holding arms and with its end that
faces the abutment element engages the pull element from behind in the
section containing the interspace.

17. Handling instrument in accordance with claim 16, wherein the holding
arms lie clamped against the upper side and the lower side of the
abutment element.

18. Handling instrument in accordance with claim 16, wherein at least one
of the holding arms enters a depression in the abutment element and is
thereby guided at the sides.

19. Handling instrument in accordance with claim 16, wherein a stop is
provided for delimiting the approach of the holding arms in the direction
of the displacement of the slide.

Description:

[0001]The present disclosure relates to the subject matter disclosed in
German application number 10 2009 004 730.1 of Jan. 15, 2009, which is
incorporated herein by reference in its entirety and for all purposes.

BACKGROUND OF THE INVENTION

[0002]The invention relates to an intervertebral implant having an
abutment element for abutment on at least one vertebral body.

[0003]Such intervertebral implants are inserted into intervertebral spaces
after removal of an intervertebral disc. To do so, it is necessary to
grasp such an abutment element with a handling instrument in order that
it can be inserted in the correct position into the intervertebral space.

[0004]The insertion is relatively easy, but difficulties may occur during
the extraction, particularly when an intervertebral implant has to be
removed again after a considerable time in situ. Considerable pulling
forces then have to be applied to the abutment element or the abutment
elements, and problems occur, particularly in the case of small
intervertebral implants in the area of the cervical vertebrae and also
when materials that do not have a very high strength are used for the
abutment element. When the abutment element is grasped directly with a
tong-shaped or clamp-type handling instrument, there is the risk that the
abutment element will break away, that pieces of material will be torn
off or that the entire abutment element will break.

[0005]The object of the invention is to so construct a generic
intervertebral implant that even when materials that do not have a high
strength are used for the abutment element, or the abutment element is of
small structural size, high pulling forces can still be applied to the
abutment element, if necessary, in order to extract it from its position
in an intervertebral space.

SUMMARY OF THE INVENTION

[0006]This object is accomplished, in accordance with the invention, in an
intervertebral implant of the kind described at the outset in that the
abutment element carries at a side edge a pull element which extends
along the side wall of the abutment element and is held on the abutment
element by pull members extending at the sides of the abutment element in
the direction towards the opposite side edge, the pull element being made
of a material whose tensile strength is greater than the tensile strength
of the material of the abutment element, and in that an interspace for
receiving a handling instrument engaging the pull element from behind is
arranged at least in a section along the pull element between the pull
element and the abutment element.

[0007]Accordingly, the abutment element is provided with an additional
pull element which extends along a side edge and has a high strength. It
is to be assumed that the tensile strength of the pull element is at
least twice as large as the tensile strength of the material from which
the abutment element is made. In particular, the abutment element may
consist of metal, for example, of titanium, but it is also possible to
use plastic materials which are compatible with the body and to produce a
pull element from carbon fiber reinforced-polyetheretherketone.

[0008]The tensile strength should lie in the range of between 500 and 3000
N/mm2, the tensile strength of titanium being about 1000 N/mm2.
In other possible metal alloys, for example, a cobalt-chromium-nickel
alloy, tensile strengths of between 800 and 2500 N/mm2 are
attainable, depending on what pretreatment has been performed. In the
case of plastic materials which are compatible with the body, the tensile
strength is significantly lower, namely, as a rule, in the range of
between 80 and 300 N/mm2.

[0009]An interspace is provided at least in a section between the pull
element and the abutment element, so that a handling instrument can
access this interspace and engage the pull element from behind. The pull
element itself is held on the abutment element by pull members engaging
the pull element at the sides and extending along the side surfaces on
the abutment element.

[0010]The pulling forces are, therefore, transmitted via the pull element
and the pull members onto the abutment element and not via any very small
parts of the abutment element itself, for example, projections which the
handling instrument engages from behind.

[0011]It is particularly advantageous for the interspace to be arranged in
the central area of the side edge, so that the pulling forces can act
centrally on the abutment element.

[0012]In a preferred embodiment, the interspace is formed by a recess in
the abutment element, which is bridged by the pull element.

[0013]It is expedient for the abutment element to have a depression above
and/or below the pull element for receiving in a guided manner a
positioning projection on the handling instrument. It is thereby ensured
that in the applied state the handling instrument is placed in a
precisely defined position relative to the abutment element, and,
therefore, lateral forces can also be applied to the abutment element by
the handling instrument, for example, in order to rotate the abutment
element about an axis of rotation extending perpendicularly to the
abutment surfaces.

[0014]It is particularly advantageous for the pull members to be joined to
one another at their ends facing away from the pull element, i.e., for
the pull element and the pull members to form a structural unit closed
within itself.

[0015]In particular, it may be provided that the pull members extend
around the outer side of the abutment element and thereby lie against its
side walls. The abutment element is thus annularly surrounded by the pull
element and the pull members, so that the introduced pulling forces
subject the material of the abutment element to pressure forces and not
to pulling forces. The risk that the abutment element will be damaged by
the application of high pulling forces is thereby reduced.

[0016]In a modified embodiment, it is also possible for the pull members
to extend inside the abutment element at their ends facing away from the
pull element. For example, they may be embedded in the material of the
abutment element.

[0017]In particular, it is advantageous for the pull element and the pull
members to be formed by an annular bandage. For example, this may be in
the form of a flat band.

[0018]Furthermore, it is expedient for a longitudinal groove in which the
pull element and the pull members are received to be provided at the side
walls of the abutment element. The pull element and the pull members are
prevented from displacement by this longitudinal groove. In particular,
when pull element and pull members in the form of an annular bandage are
used, this extends circumferentially in the longitudinal groove and,
where appropriate, may remain in this position after implantation.

[0019]Owing to the pulling forces applied to the abutment element upon
extracting the abutment element from the implantation site being
introduced into it in a distributed manner, and preferably as pressure
forces, by virtue of the described construction, the abutment element may
consist of a material which has a significantly lower tensile strength
than metal, for example, a plastic material which is compatible with the
body. In particular, polyetherether-ketone, possibly also carbon fiber
reinforced-polyetheretherketone, pyrocarbon or polyethylene with
ultrahigh molecular weight are possible.

[0020]The intervertebral implant may comprise a single abutment element,
which then has an upper outer side and a lower outer side, which are both
constructed as surfaces for abutment on adjacent vertebral bodies.

[0021]It is, however, also possible for the intervertebral implant to
comprise two abutment elements, namely an upper abutment element and a
lower abutment element, which are pivotable relative to each other. The
upper abutment element then has an upper outer side and the lower
abutment element a lower outer side, which are both constructed as
surfaces for abutment on adjacent vertebral bodies.

[0022]In a one-piece intervertebral implant, it is sufficient to provide
the single abutment element with a pull element of high tensile strength.
In intervertebral implants with an upper abutment element and a lower
abutment element, it is expedient for each abutment element to have a
corresponding pull element of high tensile strength.

[0023]The invention also relates to a handling instrument for an
intervertebral implant of the kind described hereinabove. Such a handling
instrument is characterized by having two holding arms arranged in spaced
relation to each other, between which the intervertebral implant is
arranged in such a way that the holding arms lie against the upper side
and the lower side of the abutment element, and by having mounted between
the holding arms a slide which is retractable relative to the holding
arms and with its end that faces the abutment element engages the pull
element from behind in the section containing the interspace.

[0024]An abutment element can be grasped between the holding arms with
such a handling instrument, and with the slide, which engages the pull
element from behind, for example, by means of a hook-shaped projection, a
pulling force can then be applied to the pull element, whereby the
abutment element can be extracted in its entirety from its position
without the risk of damage to the abutment element.

[0025]It is expedient for the holding arms to lie clamped against the
upper side and the lower side of the abutment element, so that the
handling instrument is positioned in a defined manner on the
intervertebral implant.

[0026]It is also expedient for at least one of the holding arms to enter a
depression in the abutment element and to thereby be guided at the sides.
Such guidance results in a precisely defined relative positioning of the
holding arms and the intervertebral implant.

[0027]Furthermore, it is advantageous for a stop to be provided for
delimiting the approach of the holding arms in the direction of the
displacement of the slide, so that when the slide is retracted, the
holding arms can be supported on the intervertebral implant. The slide
engaging the pull element from behind is thereby pressed tightly against
the pull element and already assumes a defined position in relation to
the pull element at the start of the pulling procedure.

[0028]The following description of preferred embodiments of the invention
serves in conjunction with the drawings for a more detailed explanation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 shows an intervertebral implant connected to a handling
instrument in a position in the intervertebral space between two adjacent
vertebral bodies;

[0030]FIG. 2 shows a perspective view of the intervertebral implant of
FIG. 1 connected to a handling instrument without the vertebral bodies
being represented;

[0031]FIG. 3 shows a view similar to FIG. 2 with the handling instrument
separated from the intervertebral implant;

[0032]FIG. 4 shows a sectional view taken along line 4-4 in FIG. 2;

[0033]FIG. 5 shows a perspective view of an intervertebral implant with a
pull element on both abutment elements in the form of a metallic flat
band extending around the outer side of the abutment element;

[0034]FIG. 6 shows a perspective view similar to FIG. 5 in a modified
embodiment of an intervertebral implant with an annular, band-shaped pull
element extending partially through the abutment element;

[0035]FIG. 7 shows a sectional view taken along line 7-7 in FIG. 6;

[0036]FIG. 8 shows a perspective view of an intervertebral implant with a
single abutment element and a pull element extending around it; and

[0037]FIG. 9 shows a perspective view of the intervertebral implant of
FIG. 8 seen from the opposite side.

DETAILED DESCRIPTION OF THE INVENTION

[0038]The intervertebral implant 1 shown in FIGS. 1 to 7 comprises an
upper abutment element 2 and a lower abutment element 3, which are both
of approximately plate-shaped configuration. Both abutment elements 2 and
3 lie with surface-to-surface contact against each other at bearing
surfaces. For this purpose, the lower abutment element 3 has a convex,
spherical, upwardly projecting bearing surface 4, which enters a
complementary, concave bearing surface 5 on the underside of the upper
abutment element 2. The two abutment elements 2, 3 are thus pivotable
relative to each other, so that their substantially parallel outer sides
6, 7 are adjustable in their inclination to each other. These outer sides
6, 7 form abutment surfaces on adjacent vertebral bodies 8, 9 when the
intervertebral implant 1 is pushed into an intervertebral space 10
between the two vertebral bodies 8, 9.

[0039]Intervertebral implants 1 of this type of construction are known per
se and are often made from metals which are compatible with the body, for
example, titanium, titanium alloys or cobalt-chromium-alloys. In the
present case, however, both abutment elements 2, 3 are formed from a
plastic material that is compatible with the body, for example,
polyetheretherketone, a carbon fiber reinforced-polyetheretherketone, a
pyrocarbon or an ultrahigh molecular weight polyethylene.

[0040]In the embodiment of FIGS. 1 to 5 there extends around the side
edges of both the upper abutment element 2 and the lower abutment element
3 in the longitudinal direction a circumferential groove 11 in which
there is placed a flat band 12, closed within itself, which is made of
metal, for example, of a titanium alloy. At a side edge of the upper
abutment element 2, in the illustrated embodiment at the ventral side
edge, there is provided an indentation 13 facing inwardly from the
ventral side edge, which is bridged by the flat band 12 extending in the
circumferential groove 11, so that an interspace between the flat band 12
and the material of the abutment element 2 is created by the indentation
13 behind the flat band 12 bridging the indentation 13.

[0041]There is also arranged in the area of this indentation 13 on the
outer side 6 of the upper abutment element 2 a depression 14 of
substantially rectangular cross section, whose side walls 15 extend
parallel to one another in the ventral-dorsal direction.

[0042]In a similar manner, the lower abutment element 3 has an indentation
16 and a depression 17 in the outer side 7. This depression 17 also has
side walls 18 extending parallel in the ventral-dorsal direction. This
indentation 16 is also bridged by the flat band 12 extending around the
lower abutment element 3.

[0043]On the inner side, both abutment elements 2, 3 are of flat
configuration in the area of the indentations 13, 16 and opposite the
depressions 14 and 17. These flat surfaces extend parallel to the
respective bottom 19 of the two depressions 14, 17.

[0044]An intervertebral implant of this type of construction can be
grasped by a handling instrument 20 comprising two arms 21, 22 which are
arranged in spaced relation to each other and can be bent apart in a
resilient manner. The arms 21, 22 form between them a space 23 into which
the abutment element 2 or the abutment element 3 can be pushed in such a
way that the two arms 21, 22 engage the bottom 19 of one of the
depressions 14 or 17, on the one hand, and the opposite flat inner
surface of the abutment elements 2 or 3, on the other hand. The arm of
the handling instrument 20 that is located at the outside respectively
enters the depression 14 or 17, and the side surfaces of this arm are
guided by the side walls 15 or 18 of the recesses 14 and 17. When the arm
is completely inserted, it abuts on the rear wall 24 of the depression 14
or the depression 17, so that the insertion depth is thereby delimited.
The dimensions are so selected that the two arms 21, 22 are spread apart
slightly by the abutment element 2 or 3 pushed into the space 23, and the
abutment elements 2, 3 are thereby clampingly secured in the space 23.

[0045]Between the two arms 21, 22 of the handling instrument 20 there is
mounted for displacement in the longitudinal direction of the arms a
slide 25, which carries at its end facing the free end of the arms 21, 22
a projection 26 protruding at one side. This projection 26 can enter the
indentation 13 or the indentation 16 behind the flat band 12 and, in this
way, engages from behind the flat band 12 bridging the indentation 13 or
the indentation 16. Upon further retraction of the slide 25, the flat
band 12 and thus the abutment element enclosed by the flat band 12 are
thereby firmly tensioned against the end face of the arms 21 and 22 of
the handling instrument 20. The abutment element is thereby practically
fixedly connected to the handling instrument 20. If the handling
instrument is now retracted, the pulling force can be transmitted through
the slide 25 onto the flat band 12. The pulling forces are then
transmitted by the flat band extending around the abutment element 2 as
pressure forces onto the abutment element and distributed over the
circumference, so that in spite of use of a plastic material for the
abutment element and in spite of the resulting relatively low strength of
the material there is no risk of damage occurring to the abutment element
even when high pulling forces are applied.

[0046]To apply the handling instrument to the intervertebral implant, the
slide is first advanced to such an extent that the projection 26 is
respectively pushed from the outside into the indentation, and the arms
21, 22, which are mounted on a sleeve 27 of the handling instrument 20
surrounding the slide 25, are then pushed against the abutment element
until they reach the rear wall of the respective depression. The
projection 26 of the slide 25 is thereby pushed into the indentation and
prevented from unintentionally moving out of this indentation. Even in
the case of high pulling forces, it is, therefore, ensured that the slide
25 permanently engages the flat band 12 from behind with the projection
26.

[0047]The embodiment of FIGS. 6 and 7 of the intervertebral implant is
essentially of the same construction as the embodiment of FIG. 5.
Corresponding parts are, therefore, given the same reference numerals.
Differently from the embodiment of FIG. 5, the flat band 12 in this
embodiment does not extend over its entire length on the outer side of
the abutment element, but only in the area of the ventral side edge and
in the ventral section of the two adjoining side edges extending
transversely thereto. In the dorsal section, however, the flat band 12
extends through the abutment element, i.e., it is embedded in the plastic
material of the abutment element. As is evident from this, the bandage
consisting of the flat band 12 does not necessarily need to completely
surround the abutment element, it also being possible for only
substantial portions of the abutment element to be engaged by it. A
complete encircling is nevertheless advantageous when particularly high
pulling forces have to be applied as the abutment element does then not
have to be subjected to pulling forces in sections thereof.

[0049]In contrast to this, there is provided in the intervertebral implant
of FIGS. 8 and 9 only a single abutment element 32, whose upper outer
side 36 forms an upper abutment surface and whose lower outer side 37
forms a lower abutment surface, which can both be placed against adjacent
vertebral bodies. In this implant, the abutment element is therefore a
supporting body which is pushed into the intervertebral space and extends
over the entire height of the intervertebral space.

[0050]In other respects, a construction similar to that of the two
abutment elements 2, 3 of FIGS. 1 to 7 is chosen. Corresponding parts are
therefore given the same reference numerals.